Extensible piston

ABSTRACT

A fluid pressure actuated piston is slidably carried in a fluid pressure actuated cylinder which, in turn, is slidably carried in a fixed carrier and engageable with a fixed stop to extend the range of axial movement of the piston. The fluid pressure actuated cylinder is pressurized to a retracted position until a normally closed valve member is actuated to an open position by the piston at the end of a first permissible stroke thereof in said cylinder whereupon the cylinder is pressurized into engagement with said fixed stop in the direction of movement of said piston to thereby extend the permissible stroke of the piston accordingly.

said relay including means for adjusting the length of said spring, saidsprings said force being a function of the length thereof and therebeing adjustable zero spring means acting on said beam.

US. Patant Oct. 28, 1975 EXTENSIBLE PISTON BACKGROUND OF THE INVENTIONThe present invention relates to fluid pressure actuated forcegenerating pistons having an extended range of travel.

Fluid pressure actuated pistons of the extensible type of which I amaware are not entirely satisfactory for use in aircraft disc brakes forone or more reasons as, for example, structural complexity, weight andspace requirements, operating life and reliability, maintenancerequirements and/or assembly and disassembly problems.

SUMMARY OF THE INVENTION The present invention provides a fluid pressureactuated piston particularly adapted for use in aircraft multiple discbrakes and characterized by structural simplicity, reliable operationand ease of assembly or disassembly.

The present invention provides a fluid pressure actu ated pistonslidably contained in a normally retracted pressure actuated cylinderwhich cylinder is automatically pressurized to advance the same relativeto the piston as the latter reaches a predetermined axial position inthe cylinder.

The present invention provides a fluid pressure actuated piston slidablycontained by a normally retracted fluid pressure actuated cylinder andmovable in the cylinder to a predetermined position relative thereto toactuate a valve thereby venting pressurized fluid to the cylinder whichis advanced axially relative to the piston thereby extending the rangeof piston travel accordingly.

BRIEF DESCRIPTION OF THE DRAWING The drawing represents a sectionalschematic showing a conventional fluid pressure actuated multiple discaircraft brake embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing,numeral designates an aircraft wheel and multiple disc brake therefor.The wheel is defined by two annular sections 12 and 14, only one ofwhich is fully shown, fastened together by circumferentially spacedapart bolts and nuts generally indicated by 16. The wheel is suitablyjournaled on a rotatably fixed axle 18 carried by conventional aircraftlanding gear structure, not shown. An annular brake carrier 20 suitablykeyed or otherwise secured to axle 18 is provided with a plurality ofcircumferentially spaced-part cavities 22, only one of which is shown,vented to a source of pressurized fluid, not shown, controlled by theaircraft pilot. A torque tube 24 having an integral backing plate 26suitably lined with friction material 27 is fixedly secured to brakecarrier 20 by a plurality of circumferentially spaced-apart bolts 28. Aplurality of spaced-apart annular brake rotor members 30 are suitablykeyed to a retaining member 32 fixedly secured to wheel section 12andadapted to permit axial movement of the rotor members 30 relativetowheel section 12. A plurality of annular brake stator members 34 havingfrictionlining 36. secured to opposite faces thereof are suitably keyedfor axial movement to' torque tube 24.

The cavities 22 are each provided with a sleeve or cylinder 40 slidablycontained therein and adapted to slidably contain a fluid pressureactuated piston 42. The pistons 42 are adapted to be simultaneouslypressurized and urged axially into engagement with an annular pressureplate 44 suitably keyed for axial movement to torque tube 24 whichpressure plate 44 compresses the rotor and stator members 30 and 34together against the resistance of backing plate 26 to re tard rotationof rotor members 30 and thus the wheel attached thereto. The pressureplate 44, like backing plate 26, is lined with friction material 27.

It will be recognized that the pistons 42 are necessarily confined in alimited space and must have an axial travel range sufficient tocompensate for the accumulative axial wear of the friction lining 26 and27 over a period of brake use. To that end, the present inventionprovides circular cavity 22 adapted to slidably receive cylinder 40which bottoms against an end wall 46 of cavity 22. The cylinder 40 isprovided with an end wall 48 having a central opening 50 through which atubular extension 52 integral with or otherwise fixedly secured tocarrier 20 extends. A tubular member 54 having a radially outwardlyextending flange portion 56 is slidably received by tubular extension52. The tubular extension 52 is threaded at one end thereof to receive anut 58 which acts as a stop as will be described. An 0 ring 59 disposedin a suitable recess in tubular extension 52 serves as a seal againstleakage past adjacent surfaces of tubular extension 52 and end wall 48.

The piston 42 includes a skirt portion 60 which is threaded internallyat one end thereof to receive a nut 62 which acts as a stop as will bedescribed. The skirt portion 60 is suitably recessed to receive an 0"ring 64 which provides a fluid seal against leakage past adjacentsurfaces of skirt portion 60 and cylinder 40.

The end wall 48 of cylinder 40 is exposed to an annular recess 68 whichcommunicates via a passage 70 and bore 72 of tubular extension 52 with asupply conduit 74 which conduit 74 is vented to a controlled source ofpressurized fluids not shown, under control of the aircraft pilot. Thepassage 70 is blocked by tubular member 54 which is suitably recessed toreceive spacedapart 0 rings 76 and 78 which provide a seal againstleakage of pressurized fluid past the adjacent surfaces of tubularmember 54 and tubular extension 52 to passage 70 when tubular member 54is in a retracted position as shown in FIG. 1.

The nut 62 is provided with one or more pins 80 which extendtherethrough into slidable engagement with associated recesses 66 in endwall 48 to fix the position of nut 62 rotationally relative to piston 42during assembly as will be described.

Assembly of the above-described members in the cavities 22 may beaccomplished by sliding cylinder 40 over tubular extension 52 intoposition abutting end wall 46. The nut 62 is inserted into cylinder 40and pins 64 engaged with associated recesses 66 in end wall 46. The nut58 is fastened to tubular extension 52 and tubular member 54 slippedinto tubular extension 52 to a position where flange 56 bears againstthe end of tubular extension 52 and/or nut 58. The piston 42 is insertedinto cylinder 40 and the skirt portion 60 urged into engagement with nut62.. The piston 42 may be suitably recessed, not shown. to permitengagement of a hand tool, not shown, which serves to rotate piston 42in cylinder 40 thereby screwing skirt portion 60 on nut 62 rotation ofwhich is resisted by engagement of pins 64 with end wall 46. It will beunderstood that the rings 59, 64, 76 and 78 are inserted in therespective recesses prior to assembly of the above-described members.

Assuming that the present invention is in assembled condition as shownin FIG. 1, a brake application by the aircraft pilot results inpressurization of conduit 74 from which pressurized fluid passes throughtubular members 54 into the chambers partially defined by pistons 42thereby equally pressurizing pistons 42 into engagement with pressureplate 44 which, in turn, urges rotor and stator members 30 and 34axially into engagement against backing plate 26 to produce the desiredbraking action of the wheel. It will be noted that the pressurized fluidacts against the end wall 48 of cylinder 40 thereby holding the same incontact with end wall 46 as piston 42 moves relative to cylinder 40.

Depressurization of conduit 74 results in a retraction of pressure plate44 and thus pistons 42 bearing thereagainst by virtue of conventionalretraction spring units, not shown, suitably connected to carrier andpressure plate 44.

It will be recognized that repeated brake applications in theabove-mentioned manner will result in wear of the friction materials 27and 36 necessitating a corresponding greater axial displacement ofpiston 42 which displacement of pistons 42 is normally limited by thepermissible travel in cylinder 40. Such limited displacement of pistons42 may not permit taking full advantage of the wear capability of thefriction materials 27 and 36. The present invention overcomes such anundesirable limitation by allowing piston 42 to move axially throughcylinder 40 to the extent that nut 62 engages flange portion 56whereupon continued axial movement of piston 42 causes tubular member 54to move likewise through tubular extension 52 to uncover passage 70thereby venting pressurized fluid from bore 72 to annular recess 68 andthus the entire end area of end wall 48 exposed thereto. It will benoted that there exists a significant differential effective areabetween opposite sides of end wall 48 such that with the same fluidpressure imposed on both sides of end wall 48 the resultant forceunbalance will urge cylinder 40 axially along tubular extension 52 andinto engagement with nut 58 thereby repositioning cylinder 40 relativeto piston 42. The nut 58 acts as a stop against further movement ofcylinder 40 within which piston 42 may continue to move in response topressurization thereof to the extent required to compensate for wear ofthe fric tion materials 27 and 36. The extension of cylinder 40 andcorresponding extended axial travel of piston 42 therein is believedmore than sufficient to compensate for the maximum wear capability ofthe friction materials 27 and 36.

It will be noted that the brake actuating force is derived from thepistons 42 which have a constant effective area exposed to thepressurized fluid tending to actuate the same. The constant effectivearea assures a constant force output of the pistons 42 for a given fluidpressure applied thereto throughout the range of movement of pistons 42.

I claim:

1. Extensible fluid pressure actuated piston means particularly adaptedfor use in a multiple disc aircraft disc brake provided with fixedpiston carrier means providing limited axial travel for a piston carriedthereby, said piston means comprising:

a controlled source of pressurized fluid; a fluid pressure responsivecylinder slidably carried 5 in said carrier means;

passage means communicating said cylinder with said pressurized fluid;

a fluid pressure responsive piston slidably carried in said cylinder andresponsive to said pressurized fluid for actuating said disc brake;

normally closed valve means operatively connected to said passage meansfor controlling pressurized fluid flow therethrough to said cylinder;and

fixed stop means connected to said carrier means;

said piston being actuated by said pressurized fluid to a predeterminedposition in said cylinder and into operative engagement with said valvemeans to actuate the same to an open position thereby pressurizing saidcylinder to actuate the same axially relative to said piston and intoengagement with said fixed stop thereby extending the range of travel ofsaid piston in said cylinder accordingly.

2. Extensible fluid pressure actuated piston means as set forth in claim1 wherein:

said fixed stop means includes a tubular extension fixedly secured atone end to said carrier means and slidably extending through an end wallof said cylinder; and

a stop member removably secured to the free end of said tubularextension and engaged by said cylinder.

3. Extensible fluid pressure actuated piston means as set forth in claim2 wherein:

said valve means is a tubular member slidably carried by said tubularextension for axial movement therethrough and adapted to be engaged bysaid piston.

4. Extensible fluid pressure actuated piston means as set forth in claim3 wherein:

said tubular member is provided with a radially extending flange at oneend thereof;

said piston is provided with a skirt portion adapted to surround saidtubular extension and having a radially inwardly extending annular endportion adapted to engage said flange.

5. Extensible fluid pressure actuated piston means as claimed in claim 3wherein:

said tubular member normally blocks said passage means and is providedwith axially spaced-apart annular seal means to prevent leakage of saidpressurized fluid through said passage means.

6. Extensible fluid pressure actuated piston means as claimed in claim 2wherein:

said end wall is exposed on a first side to said passage downstream fromsaid valve means and on a second side to said pressurized fluid;

said first and second sides having a differential effective area andcorresponding force unbalance whereby said cylinder is held in aretracted position 60 until said valve means is opened to vent saidpressurized fluid to said first side to reverse the force unbalanceacting on said cylinder thereby actuating the same into engagement withsaid fixed stop. 7. Extensible fluid pressure actuated piston means asclaimed in claim 4 wherein:

said radially inwardly extending annular end portion is an annularmember having screw threads formed on the radially outermost sidethereof;

ing pins adapted to slida'bly engage mating openings in said end wall toretain said annular member against rotational movement therebyfacilitating assembly of said piston and said annular member.

1. Extensible fluid pressure actuated piston means particularly adaptedfor use in a multiple disc aircraft disc brake provided with fixedpiston carrier means providing limited axial travel for a piston carriedthereby, said piston means comprising: a controlled source ofpressurized fluid; a fluid pressure responsive cylinder slidably carriedin said carrier means; passage means communicating said cylinder withsaid pressurized fluid; a fluid pressure responsive piston slidablycarried in said cylinder and responsive to said pressurized fluid foractuating said disc brake; normally closed valve means operativelyconnected to said passage means for controlling pressurized fluid flowtherethrough to said cylinder; and fixed stop means connected to saidcarrier means; said piston being actuated by said pressurized fluid to apredetermined position in said cylinder and into operative engagementwith said valve means to actuate the same to an open position therebypressurizing said cylinder to actuate the same axially relative to saidpiston and into engagement with saiD fixed stop thereby extending therange of travel of said piston in said cylinder accordingly. 2.Extensible fluid pressure actuated piston means as set forth in claim 1wherein: said fixed stop means includes a tubular extension fixedlysecured at one end to said carrier means and slidably extending throughan end wall of said cylinder; and a stop member removably secured to thefree end of said tubular extension and engaged by said cylinder. 3.Extensible fluid pressure actuated piston means as set forth in claim 2wherein: said valve means is a tubular member slidably carried by saidtubular extension for axial movement therethrough and adapted to beengaged by said piston.
 4. Extensible fluid pressure actuated pistonmeans as set forth in claim 3 wherein: said tubular member is providedwith a radially extending flange at one end thereof; said piston isprovided with a skirt portion adapted to surround said tubular extensionand having a radially inwardly extending annular end portion adapted toengage said flange.
 5. Extensible fluid pressure actuated piston meansas claimed in claim 3 wherein: said tubular member normally blocks saidpassage means and is provided with axially spaced-apart annular sealmeans to prevent leakage of said pressurized fluid through said passagemeans.
 6. Extensible fluid pressure actuated piston means as claimed inclaim 2 wherein: said end wall is exposed on a first side to saidpassage downstream from said valve means and on a second side to saidpressurized fluid; said first and second sides having a differentialeffective area and corresponding force unbalance whereby said cylinderis held in a retracted position until said valve means is opened to ventsaid pressurized fluid to said first side to reverse the force unbalanceacting on said cylinder thereby actuating the same into engagement withsaid fixed stop.
 7. Extensible fluid pressure actuated piston means asclaimed in claim 4 wherein: said radially inwardly extending annular endportion is an annular member having screw threads formed on the radiallyoutermost side thereof; said piston skirt portion having a threadedportion adapted to receive said annular member.
 8. Extensible fluidpressure actuated piston means as claimed in claim 7 wherein: saidannular member is provided with axially extending pins adapted toslidably engage mating openings in said end wall to retain said annularmember against rotational movement thereby facilitating assembly of saidpiston and said annular member.